1. Field of the Invention
This invention relates to a method for producing a fibrous web, in particular a paper web or paperboard web, from at least one fibrous suspension in a twin mesh former with a twin mesh zone which has a wedge-shaped intake nip and is formed at least in some sections by two rotating endless meshes, of which the first mesh, which is passed over a preferably positionable inlet roller, is passed in the double mesh zone over several rails rigidly arranged a distance from each other on a preferably movable dewatering box, and of which the second mesh is passed in the twin mesh zone over several rails which are arranged opposite the rails of the preferably movable dewatering box, are supported by means of compliant elements and are pressed with a selectable force against the second mesh.
In addition, the invention relates to a twin mesh former of a machine for producing a fibrous web, in particular a paper web or paperboard web, from at least one fibrous suspension, and to a sheet forming system of a machine for producing a preferably multi-layer fibrous web, in particular a paper web or paperboard web, from at least one fibrous suspension.
2. Description of the Related Art
A twin mesh former, known among those skilled in the art as a “hybrid former”, is described in the German publication DE 40 02 304 A1.
It is characteristic of said type of former that the inlet, in particular the inlet conditions and the inlet geometries, of the fibrous suspension into the twin mesh zone in the region of the inlet gap are particularly important. Serious faults in the sheet forming, in particular on the upper side of the fibrous web to be formed, are often caused at this point. An example of such faults are bright spots.
Attempts have been made to reduce these faults by changing the so-called angle of intersection, but the effect of said measure was more than unsatisfactory under certain conditions such as excessively high turbulence on the mesh. The angle of intersection is defined here to mean the angle at which the first mesh intersects with the fibrous suspension lying on the second mesh at the point of intersection.
What is needed in the art is a method, a twin mesh former, and a sheet forming system such that faults are largely effectively prevented in particular during the initial sheet forming process in the region of the point of intersection even under difficult conditions.